1. Field of the Invention
The instant disclosure relates to an image capturing module and an image sensing unit thereof, and more particularly to an image capturing module and an image sensing unit thereof for increasing the image quality.
2. Description of Related Art
Recently, it becomes more and more popular for portable devices such as mobile phones or PDA to be equipped with an imaging module. Furthermore, since the market requires these portable devices to have more powerful functions and smaller sizes, it is necessary for the imaging module to generate high quality pictures and to be of small size accordingly. One improvement of picture quality is to increase the number of pixel. The pixel number of an imaging module has already increased from the VGA-level 30 pixels to 2, 5, 8, 13 or even 41 million pixels, which is now common in the market. Another improvement lies in the definition of the image. Thus, the imaging module of a portable device also develops from a fixed-focus mode to auto-focus mode or even optical zoom mode.
The auto-focus mode employs the principle of moving the lens in the imaging module suitably according to various distances of targets, whereby the optical image of the desired target can be focused correctly on an image sensor so as to generate a clear image. The common ways of activating the lens to move in the imaging module include activating by a stepping motor, piezoelectric motor and voice coil motor (VCM). However, when light source is not enough, the image quality provided by the imaging module would be decreased.